Technologies, such as multiple-input multiple-output (MIMO) and transmit diversity, have been developed to enhance the data throughput on the downlink. Data transmission requirements on the downlink are normally larger than those on the uplink. Transmit diversity and MIMO are also considered for the uplink, which would provide extended coverage and enhanced data rate for the uplink such that the peak data rate imbalance between the downlink and the uplink would be reduced.
With the evolution from single antenna transmissions to dual- or multi-antenna transmissions, additional data throughput enhancement would be possible. In order to support the dual- or multi-antenna transmissions in the uplink, it would be required to design a control channel for carrying pilot and other control information on the second transmit antenna.